Possible bug in symbolic observations of openable entities

[rikifunt]

Hi,

I think there might be a bug in observations.symbolic (https://github.com/epignatelli/navix/blob/main/navix/observations.py#L101), which makes locked and open doors have identical observations. Currently, the relevant lines that compute the observation (https://github.com/epignatelli/navix/blob/main/navix/observations.py#L132) are:

        if isinstance(entity, Openable):
            entity_state = entity.open + (entity.requires != jnp.zeros(entity.shape))

Which means entity_state will be 1 if the door is either open or locked, and 0 when it is closed but does not require anything to be opened. Is this the intended behavior? From my understanding of the docstring of the function, it should instead be something like:

        if isinstance(entity, Openable):
            entity_state = (1 - entity.open) + (entity.requires != jnp.zeros(entity.shape))

which results in:

• 0 if the door is open
• 1 if the door is closed but has no requirements
• 2 if the door is locked and requires a key

If this is the case, I can also submit a PR with a fix if needed. Thank you.